The following reasons may cause your iOS device unrecognizable:
1) iTunes is not installed properly, so the device is not detected by iTunes.
2) Apple Mobile Device service is not started.
3) The password of the screen is locked and the device doesn't have trust authority.
4) The iOS version is lower than iOS 6.
5) iCloud is open when you connect the device with the computer.
To fix it, please connect your device to computer again and restart the program. Then provide the following information for us to check why FonePaw can't detect your iPhone:
1) What is your iTunes version? Can iTunes detect your iPhone?
2) What is your device and iOS?
3) What is the OS of your computer?
4) Send us the screenshot of FonePaw iOS Transfer.
5) Submit the log file through feedback section in FonePaw iOS Transfer.